These studies are directed at a better understanding of the behavioral effects of drugs acting on dopamine neurotransmission. Several previous studies had results indicating that selective D1 or D2 dopamine agonists and antagonists were not functioning as they would be expected based on their in vitro pharmacology. Subsequent studies have been directed at quantitative assessments of behavioral effects of agonist-antagonist interactions. These studies have utilized several different behavioral endpoints, including grossly observable behavior, locomotor activity, consummatory behavior, learned operant behavior, and drug discrimination. In addition, a series of studies is examining the behavioral effects of drugs that are thought to bind irreversibly to the dopamine transporter. These studies will provide answers to several basic questions regarding the functioning of this site as well as provide information that may be of use in the development of drugs to treat cocaine abuse. Finally, studies are being conducted that address the interactions of the dopamine system with cholinergic and GABAergic systems.